Effect of nano and micro SiC particles on the microstructure and fracture toughness of ZrB2-SIC nanocomposite produced by SPS method

In this research, effect of SiC particles size on the microstructure, densification and fracture toughness of ZrB2-SiC composite prepared by spark plasma sintering (SPS) method was evaluated. For this purpose, ZrB2-30vol% SiC composites were consolidated by SPS method, using SiC powders with different initial particle sizes (45 nm, 80 nm and 25 mu m). Scanning Electron Microscopy (SEM) was used to study the microstructural evolutions. Relative density and open porosity were measured by Archimedes .In order to evaluate the fracture toughness and toughening mechanisms, the SENB method and the crack growth resulted from the Vickers indentation were used respectively. The results showed that by reducing the size of the initial SiC particles from the micrometer scale to the nanometer scale, the size of the ZrB2 matrix grains also decreased, which led to increase the relative density. Also, applying nano-SiC particles compared to micrometer, led to considerable increase in the fracture toughness. Microscopic examination of the crack propagation path from Vickers indentation effect showed that crack deviation and crack branching were activated as the most important toughening mechanisms in ZrB2-SiC composites.